Insulin
Insulin is a hormone produced by the beta cells of the pancreas. Insulin delivered into the body through a syringe, insulin pen, or other delivery method is known as exogenous insulin. The role of exogenous insulin in treating diabetes mellitus was first discovered, and the substance refined, in 1921 at the University of Toronto by Sir Frederick Banting, and colleagues Best, Collip, and Mcleod. Commercial production began in 1923 at the newly formed Nordisk Insulin Labs (now Novo Nordisk) in Denmark, and at Eli Lilly and Co. in the USA. Insulin is necessary to enable the body to perform normally. It allows cells to use glucose found in the bloodstream, thus preventing hyperglycemia. In the cells themselves, insulin aids in the anabolic (a positive, building or maintaining process) processes of turning glycogen stored in the liver and in muscles, into energy, and helps transform fatty acids and protein into forms both useful and necessary to the body. It prevents or counter-acts the negative or destructive catabolic body processes of gluconeogenesis, fat and glycogen breakdown. Insulin, then, in 10 words or less, is the hormone that lowers blood glucose. And if you read no further, it would appear that as long as one has some insulin, either endogenous or exogenous, this is simple and everything will be fine. There are other hormones present and also necessary to the body, which do the exact opposite of insulin--raising blood glucose levels. Cortisol,growth hormone, adrenalin AKA epinephrine, glucagon, progestrone and thyroid hormone are considered counter-regulatory hormones as far as diabetes and blood glucose levels are concerned. They need just as much consideration as insulin, because changes in their bloodstream levels, can mean a possible interference with insulin. These changes can occur normally within the body, as symptoms of a disease state (Acromegaly=too much growth hormone, Cushing's Disease=too much cortisol/cortisone, Hyperthyroidism=too much thyroid hormone), or as a result of other medications, such as steroids. The counter-regulatory hormones such as adrenalin/epinephrine, glucagon and cortisol/cortisone are released by the body if it believes it's threatened with hypoglycemia. This is part of the body's "self-defense" mechanism to counter the effects of too much insulin. So there's more just insulin one needs to think about. It's vital to life whether enough is produced by the body or whether it's injected. The other hormones are also vital to the body and being able to understand how the various hormones react or interact with each other is very helpful in understanding and successfully controlling diabetes. These are the various insulins discussed on this site. Strength The strength of an insulin is measured in International Units (IUs) of insulin per millilitre (ml). The two most common strengths used in pets are U40 (40 units insulin per ml) and U100 (100 units insulin per ml). U100 insulins are developed primarily for use in humans, although they are commonly used in pets. U40 insulins were commonly available in the US until the 1980's, along with the now-standard U100 strength. They are still available in some countries, but have been phased out in many, in favor of U100. U40 insulins are able to be drawn and dispensed in smaller doses (less than 5 units) with much greater accuracy than their U100 counterparts. This makes them advantageous for use in treating both children and pets, who both have smaller bodies and smaller insulin requirements than adult humans. U40 insulin has its advantages for more than children and pets. The hexamers of insulin tend to associate with each other (stay together); they cannot be readily absorbed while they remain this way. Diluting insulin into U40 strength forces them into dissociating (staying apart from each other), which means they are absorbed better and more rapidly. This study compares the absorption rate of U100 and U40 insulins. The findings show U100 insulin to be significantly slower acting than U40 because it has a slower absorption rate. U40 insulin was also the subject of another 1998 study. This one compared it to both U100 insulin and the rapid-acting analog insulin Lispro (The only one marketed at the time.) Insulin lispro, known as Humalog, was found to be only slightly more rapidly absorbed than U40 non-analog insulin. The fact that U40 insulin has a similar pharmacokinetic profile to analog insulin, has not been lost on the German Institute for Health Care Quality (government department). At present, they propose a cost-cutting move which would stop prescription coverage of the rapid-acting analogs for all newly-diagnosed Type 2 diabetics in Germany. Types by length of action Insulins are categorized first by length of action, then by origin and by suspension. The five durations are: * Rapid onset-fast-acting insulin * Short-acting insulin * Intermediate-acting insulin * Mixed insulin * Long-acting insulin The usual times for onset, peak, and duration are found with the information for the insulin itself, but they also depend on the species, the suspension, and the individual. In particular, a given insulin that lasts, say, 20 hours in humans or dogs is more likely to last 10 hours in cats due to cats' faster metabolism. So the times found here are average for humans and dogs, but will last less time in cats. This insulin chart is a bit dated, but seems to be a good guide to onset, maximum effect (peak) and duration. Looking at NPH for both dogs and cats gives example of cats' faster metabolism; its expected duration for cats is half that for dogs. Types by origin Insulins differ by species. Most commonly available types are: * r-DNA human insulin * Genetically-engineered (GE) human insulin * Genetically-modified (GM) human insulin * porcine (pork) insulin * bovine (cow) insulin * human analog insulins Porcine insulin is identical to canine. Bovine insulin is similar to feline, differing by only a single amino acid in position 18. (Mnemonic device: pi'G' = do'G', 'C'ow = 'C'at). Both differ in up to four amino acids (positions 8, 10, 18, 30) from natural human insulin.http://www.petdiabetes.org/insulin_sequence.htm Porcine (pig) and bovine (cow) insulins can be combined to produce a "blended" insulin (such as Iletin I (beef/pork) and PZI Vet). Genetically-engineered artificial insulins with different amino acid composition such as Lantus, Levemir, Humalog, Novolog, and Apidra, are known as analog insulins. Types by suspension The suspension (liquid the insulin is suspended in) is the key to its activity over time. Typical suspensions are Isophane (NPH), Zinc (Lente, Ultralente) and Protamine Zinc (PZI). In general, all insulins with the same suspension will have a similar time activity profile and behave similarly. In non-analog insulins, it is the suspension that makes intermediate and long-acting types work longer than R/neutral. This is one reason why insulins should be diluted only with the correct approved diluent for that insulin. Guidance on use See injecting insulin, rolling insulin, and diluting and combining insulin. For dosage see Regulation. Note that any insulin, given in overdose, can lead to hypoglycemia and coma or death. For advanced use see also basal, bolus, and booster. For what can go wrong with insulin see Obstacles to regulation Damaged insulin section. External Links *More details on insulin types for animal use *More general insulin information :Good illustrations and charts for seeing where bovine and porcine insulins differ from human insulin and how analog insulins Lantus (insulin glargine), Novolog (insulin aspart), and Humalog (insulin lispro) have been altered to produce their respective effects. Some absorption discussion related to humans, some of which is relevant to animals, as absorption is an important factor in how the insulin is used for all with diabetes. Time activity profiles for everything except Levemir and any PZI. Aspart/Lispro chart would be applicable for the new Aventis Apidra, as it is also a rapid-acting insulin designed for bolus in humans. *The History of Insulin *The Discovery of Insulin *Meet FREDFaculty Research Expertise Database at PennState's College of Medicine. *Time Activity Profile Tables for human approved insulins sold outside of North America *Diabetes control in Siberian Husky Case details about using R/neutral and/or mixed insulins in dogs. *A chart of the variations in amino acid sequence on the A and B chains of different species. *Dr. Ragnar Hanas is a Swedish pediatrician whose book about Insulin-Dependent Diabetes is clearly written and easy to understand. Unlike many doctors, you feel she's talking with you and not down to you. Even though it was written in 1999 and insulins Lantus and Levemir were not yet marketed, the explanations are classic. She intended it for explaining human diabetes, but there is much we can gain from it too. The link is to a chapter she graciously donated to Children With Diabetes. *Click Here To View Time Activity Profiles of Lilly Insulins Category:InsulinsCategory:Treatments Category:Terms